[RookieSQ]

First post here. Forgive me if this is a redundant question.

I currently own a set of CSS EL70 mids with mods by Planet10 Audio. I would like to use these in an OB configuration with another driver taking care of low frequency duties. In an ideal world, I'd like this speaker to be 12" wide or less due to WAF. And for asthetic reasons, I'm going to build the baffle from acrylic (just the EL70). Budget is also a concern, I'd like to keep the woofers under $200 total. Less would be better!

Will a single 12" woofer provide enough output or should I consider using a sealed/vented enclosure for the sub? I listen to just about everything (classical, rock, metal, rap, dance.........).

This system will be passive.

[JCS]

I will give my standard reply:

There are at least two schools of thought on OB design: wide baffle & narrow baffle.  I subscribe to the wide baffle camp. Check out MJK's web site:
http://www.quarter-wave.com/OBs/OB_Theory.html

Cheers, Jim

[mcgsxr]

I would say that what you are considering can be done, though I have never done it personally.

There are many examples of baffles that are slimmer around the mid/high than the bass.  You may consider "wings" for the sub, that will help dramatically.

I would personally recommend biamping the sub, but only as I had great success that way.  It can be done passively with a single amp, but it requires careful woofer and single driver combinations.

Agree that the s/w referenced will help you design it.

I highly recommend playing with mdf to test mule baffle size and shape before committing the $ to acrylic baffles.

Good luck, and have fun!

[motosapien]

Unfortunate that they no longer make the EL 70, it was a very good full range driver.  I found the rising response needed a filter.  What worked well for me was a .60mf inductor with a 5 ohm resistor across it on the hot leg.  I wonder though if that driver is not efficient enough to work well in an ob?  Perhaps  Matevena would weigh in here.  Seems I recall it is about 84 spl or so.

I'm in the process of building  the  Hestia's upper two drivers before experimenting with the bass integration.

[RookieSQ]

The mid is 86db 1w/m
I am also able to use a 15" woofer now(Eminence 15a is sold at a retailer not far from me).

I will be going passive to start, but am seriously considering active in the future.

For what it's worth, I would like the woofer baffle to be a cylinder. Like an H or U frame, just not square. This is another cosmetic decision, so if this is against a "rule" of OB design, please let me know.

I will be making a few samples of the baffles (mid and woofer) before making any final decisions.

[MJK]

For what it's worth, I would like the woofer baffle to be a cylinder. Like an H or U frame, just not square. This is another cosmetic decision, so if this is against a "rule" of OB design, please let me know.

Other people have done this and it works great. There is a picture of just such a design in my gallery.

http://www.quarter-wave.com/Gallery/Gallery.html

Scroll down a few times until you find the black tubed H frame.

[RookieSQ]

Other people have done this and it works great. There is a picture of just such a design in my gallery.

http://www.quarter-wave.com/Gallery/Gallery.html

Scroll down a few times until you find the black tubed H frame.

That's excellent. Thanks.
How can I determine the minimum width of the mid baffle and the size of the H frame?
It looks like the 15a is a very popular woofer for OB, so I'm sure I can follow in others foot steps there?

[MJK]

H frame size, baffle width and shape, driver position in the OB, and crossover points and slopes all combine to form the system SPL response. You can build and listen using a trial and error approach based on yours and others experiences or you can do the engineering design simulations to arrive at a unique design that is all your own. Those are the two extremes and both work, I use the latter approach.

[RookieSQ]

I would like to do as much of the design on paper as I can before I start building. But I have no design experience, so I'll be leaning on you guys for help with that. The construction part it's much simpler for me.

Is there a general rule if thumb to start with or calculators available?
I suppose I'll need to start another design/build thread for this however.

[Chicken Man]

I was hoping to improve the directivity of my open baffle design for my home theatre and over the last 2 nights I was experimenting with acoustically absorbing much of the rear wave from the front of speaker.

Using carpet underlay (cotton felt )about 1/2 inch thick to absorb the middle range frequencies from the rear of each loudspeaker it significantly improved the overall definition of the dialogue and the sound in general.

So it seems minimizing the delayed room reflections from the rear of the loudspeaker while still allowing it to breathe as an open baffle, only adds to that bonus of clarity and fast transients indicative of open baffle design.

A real positive worth considering and it is quite simple to apply,and may work for you as it did for me.

I use a 270mm wide baffle (10 1/2 inch) in a 3 way passive OB design with a subwoofer.

C.M

 

[Chicken Man]

After much consideration and extended listening, experimentation showed that absorbing the rear wave of an open baffle loudspeaker actually is to no benefit but is rather detrimental to its overall sound character perceived in a room, so discount what was said in the above post.
It didn't work as I first perceived it had, just part of the learning curve I guess.   

C.M

[FullRangeMan]

Rooms to planars or to dipoles have to be live(hard surfaces).